The present invention relates to self locking paperboard containers of the telescoping tray and cover type. Such containers are well known in the art and are used extensively for packaging products for shipment and storage.
Various approaches have been taken by those skilled in the art to design and produce self locking containers as disclosed herein. However, in most instances, the containers have required a considerable amount of paperboard with extra panels, flaps and tabs to achieve the desired self locking feature.
As examples, U.S. Pat. No. 3,247,955 illustrates an interlocking package which requires the use of two interlocking members which are telescoped within an outer surrounding wrapper. U.S. Pat. No. 2,800,266 shows a container body with outwardly folded locking flanges on the upper edges of the side walls which become engaged with matching inwardly folded locking flanges on the lower edges of the sides of a cooperating end cap. The locking flanges in each case are extra flaps which have no purpose other than to lock the cap on one end of the container body. U.S. Pat. No. 3,115,292 illustrates a multi-wall bulk pack consisting of an outer shell with locking flaps foldably attached to and folded outwardly of the lower edges thereof. When the cap is wedged between the outer shell and inner liner the locking flaps on the shell and cap become engaged to lock the components together. However, as in the case of the aforementioned patent, the locking flaps on the cap and shell are non-functional except for their locking action. Meanwhile, in U.S. Pat. No. 4,114,798, extra tab sections are provided on the corner glue flaps for the cover element of the container which are reversely folded to engage extra flaps provided on the tray element when the two elements are telescoped together. Thus it may be seen that the prior art self locking containers are complicated in construction and use.
In contrast to the above, the self locking container of the present invention requires only a minimum amount of paperboard for its construction since it employs elements normally used in the construction of the components for performing the self locking feature. In addition, the present invention provides the self locking features applied to a collapsible, leak proof container with means for providing access to the self locking elements for effectively releasing the elements when it is desired to open the container, and means for retaining the normally collapsed walls of the container in an upright condition for use.